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      <title>ThreadLocal - 交互式测验</title>
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      </style>
    </head>
    <body>
      <div class="main-wrapper">
          <div class="quiz-container">
            <div class="quiz-header">
              <h1>ThreadLocal - 交互式测验</h1>
              <p>检验你对文档内容的理解程度</p>
            </div>
            <div id="quiz-content">
                <div class="quiz-body">
                    <div class="progress-bar">
                        <div id="progress-indicator"></div>
                    </div>
                    <div id="question-container">
                      <p id="question-text"></p>
                      <ul class="options-list" id="options-list"></ul>
                    </div>
                    <div id="result-container"></div>
                    <div id="hint-container" class="hint-container"></div>
                </div>
                <div class="quiz-footer" id="quiz-footer">
                  <button id="prev-btn" class="nav-btn">上一题</button>
                  <button id="hint-btn" class="nav-btn" style="background-color: #ffc107; color: #333; box-shadow: 0 4px 12px rgba(255,193,7,0.3);">提示</button>
                  <button id="next-btn" class="nav-btn">下一题</button>
                </div>
            </div>
          </div>
      </div>

      <script>
        const quizData = [
  {
    "question": "根据文档，`ThreadLocal` 的核心设计目的是什么？",
    "options": [
      "为了在多个线程之间安全、高效地共享同一个变量。",
      "为每个线程提供一个独立的变量副本，从而实现线程间的数据隔离。",
      "用于替代 `synchronized` 关键字，提供一种更高性能的锁机制。",
      "管理线程池中线程的创建、执行和销毁等生命周期。"
    ],
    "correctAnswerIndex": 1,
    "explanation": "`ThreadLocal` 的设计初衷是为每个线程提供一个独立的变量副本。文档中将其比喻为“每个线程的‘私人订制’变量”或“自己的小隔间”，其核心价值在于线程隔离，而不是数据共享或同步。",
    "source": "文档中「ThreadLocal的基本概念」部分",
    "hint": "文档中将其比作办公室里每个员工都有的'小隔间'，思考一下'小隔间'的作用是什么？"
  },
  {
    "question": "`ThreadLocal` 是如何实现为每个线程存储独立副本的？其背后的关键数据结构是什么？",
    "options": [
      "它使用一个全局的、线程安全的 `ConcurrentHashMap<Thread, T>` 来存储数据。",
      "它依赖于一个名为 `ThreadLocalMap` 的内部类，这个Map实际上是每个 `Thread` 对象自身的成员变量。",
      "它将变量值直接作为 `Thread` 类的一个新字段进行存储。",
      "通过操作系统的原生线程支持，在每个线程的栈内存中分配一块特殊区域。"
    ],
    "correctAnswerIndex": 1,
    "explanation": "文档明确指出，`ThreadLocal` 的实现依赖于其内部类 `ThreadLocalMap`。这个Map并非存在于`ThreadLocal`对象中，而是作为每个`Thread`对象的一个属性（`threadLocals`）。当操作`ThreadLocal`变量时，实际上是在操作当前线程内部的`ThreadLocalMap`。",
    "source": "文档中「ThreadLocalMap」部分",
    "hint": "文档中提到一个类是 `ThreadLocal` 的“幕后英雄”，它负责管理每个线程的变量副本。"
  },
  {
    "question": "当在一个线程中首次调用一个`ThreadLocal`变量的`get()`方法，且之前没有调用过`set()`方法，会发生什么？",
    "options": [
      "该方法会返回 `null` 或通过重写 `initialValue()` 方法指定的初始值。",
      "该方法将抛出 `NullPointerException`，因为值尚未初始化。",
      "线程将被阻塞，直到其他线程为该变量设置一个值。",
      "会返回上一个结束的线程在该 `ThreadLocal` 中留下的值。"
    ],
    "correctAnswerIndex": 0,
    "explanation": "如果在调用 `get()` 时，当前线程的 `ThreadLocalMap` 中不存在该 `ThreadLocal` 变量的条目，系统会调用 `initialValue()` 方法来获取一个初始值。`ThreadLocal` 类中这个方法的默认实现是返回 `null`，但开发者可以重写它来提供自定义的默认值。",
    "source": "文档中「initialValue()方法」和「get()和set()方法」部分",
    "hint": "文档中提到了一个方法，它就像是 `ThreadLocal` 的'初始设置'，在第一次访问时被调用。"
  },
  {
    "question": "在长期运行的服务（如使用了线程池的Web应用）中使用`ThreadLocal`时，需要特别注意哪个潜在问题？",
    "options": [
      "死锁风险，因为`ThreadLocal`内部有复杂的加锁逻辑。",
      "内存泄漏，因为线程可能被复用，但之前存储在`ThreadLocal`中的对象未被清理，导致其无法被垃圾回收。",
      "性能瓶颈，因为频繁读写`ThreadLocal`会导致线程上下文切换。",
      "数据不一致，因为`ThreadLocal`无法保证跨线程的可见性。"
    ],
    "correctAnswerIndex": 1,
    "explanation": "文档在“内存管理”部分强调，当线程的生命周期比`ThreadLocal`变量的生命周期长时（例如在线程池中），如果不手动清理，`ThreadLocal`中存储的对象引用会一直存在，即使业务逻辑上已经不再需要它，从而导致内存泄漏。",
    "source": "文档中「内存管理」部分",
    "hint": "文档作者分享了一个教训：在一个“长期运行的服务”中，因为没有及时做什么而导致了问题？"
  },
  {
    "question": "根据文档，以下哪个场景是`ThreadLocal`的典型应用？",
    "options": [
      "实现一个全局共享的、高并发访问的缓存系统。",
      "统计网站的总访问人数，需要所有线程更新同一个计数器。",
      "在Web应用中，为每个HTTP请求线程保存独立的会话信息（Session）或数据库连接。",
      "在生产者-消费者模型中，用于存放共享任务的阻塞队列。"
    ],
    "correctAnswerIndex": 2,
    "explanation": "文档在“ThreadLocal的应用场景”部分明确列举了几个适合的场景，包括数据库连接池和会话管理。这些场景的共同特点是需要为每个独立的执行单元（线程）维护一个隔离的资源或上下文，以避免线程间的资源竞争和状态干扰。",
    "source": "文档中「ThreadLocal的应用场景」部分",
    "hint": "思考一下文档列举的三个应用场景（数据库连接池、会话管理、缓存）有什么共同的特点？"
  },
  {
    "question": "当调用 `myThreadLocal.set(value)` 时，这个键值对（`myThreadLocal`实例作为键，`value`作为值）最终存储在哪里？",
    "options": [
      "存储在 `myThreadLocal` 对象内部的一个 `HashMap` 中。",
      "存储在当前线程（`Thread.currentThread()`）所持有的 `ThreadLocalMap` 对象中。",
      "存储在一个由JVM管理的、全局共享的静态区域中。",
      "直接作为当前线程对象的一个动态添加的成员变量。"
    ],
    "correctAnswerIndex": 1,
    "explanation": "`set()` 方法的逻辑是：首先获取当前线程 `Thread.currentThread()`，然后获取该线程内部的 `ThreadLocalMap`，最后将当前的 `ThreadLocal` 实例作为 key，要设置的 `value` 作为 value，存入这个 map 中。因此，数据是与线程绑定的，而不是与 `ThreadLocal` 对象绑定。",
    "source": "文档中「get()和set()方法」和「ThreadLocalMap」部分",
    "hint": "`set(T value)` 方法的第一步是 `Thread t = Thread.currentThread();`，这暗示了数据将与哪个对象关联？"
  }
];
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                // 高亮正确答案
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            const totalQuestions = quizData.length;
            const answeredCount = userAnswers.filter(a => a !== null).length;
            const wrongCount = answeredCount - correctCount;
            const skippedCount = totalQuestions - answeredCount;
            const accuracy = totalQuestions > 0 ? Math.round((correctCount / totalQuestions) * 100) : 0;
            const errorRate = totalQuestions > 0 ? Math.round((wrongCount / totalQuestions) * 100) : 0;

            const finalScoreHtml =
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                '<h2>答题报告</h2>' +
                '<div class="score-summary">' +
                '<div class="score-card">' +
                '<h3>得分</h3>' +
                '<p>' + correctCount + ' / ' + totalQuestions + '</p>' +
                '</div>' +
                '<div class="score-card">' +
                '<h3>正确率</h3>' +
                '<p>' + accuracy + '%</p>' +
                '</div>' +
                '<div class="score-card">' +
                '<h3>错误率</h3>' +
                '<p>' + errorRate + '%</p>' +
                '</div>' +
                '<div class="score-card score-details">' +
                '<table>' +
                '<tr><td>正确</td><td>' + correctCount + '</td></tr>' +
                '<tr><td>错误</td><td>' + wrongCount + '</td></tr>' +
                '<tr><td>未答</td><td>' + skippedCount + '</td></tr>' +
                '</table>' +
                '</div>' +
                '</div>' +
                '<div class="report-actions">' +
                '<button id="review-btn">回顾测验</button>' +
                '<button class="primary" onclick="location.reload()">再试一次</button>' +
                '</div>' +
                '</div>';

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        nextBtn.addEventListener('click', goToNextQuestion);
        hintBtn.addEventListener('click', showHint);
        
        // 初始加载
        loadQuestion();
      </script>
    </body>
    </html>
  